Resources System

What is Resources?

It takes more than just code to build a great app. Resources are the addi8onal files and sta8c content that your code uses, such as bitmaps, layout defini8ons, user interface strings, anima8on instruc8ons, and more.

What is Resources?

A Storeroom contains pieces of data needed in applica8on •  Image (jpg, png) •  Layout (xml) •  etc.

What is Resources?

Java Source Codes

Resources

What is Resources?

Source Code Resources Running Applica5on

= + +

+

What is Resources?

How does Resources System look like? You should always externalize resources such as images and strings from your applica8on code, so that you can maintain them independently

Resources Sources

App-Specific Resources System Resources

What is Resources?

+

It’s awesome It works

Resources Type

Drawable Something that can be

drawn on screen

Layout XML contains Layout hierarchy/

structure

Menu Context menu, Popup menu

Values Strings, Colors, Dimension, etc.

Anima8on XML contains Property

anima8on or View anima8on

etc. Almost everything but Java

source codes

Resources Type: Drawable

• A drawable resource is a general concept for a graphic that can be drawn to the screen •  folder res/drawable • Have A LOT to be learned, be

prepared …

Playaround: ImageView

… Play Play Play …

How to refer resource from another resource?

… Play Play Play …

Rule 11: Each resource folder couldn’t have any child folder. Manage filename wisely.

The R class: How are Resources compiled?

Filename will be simply automa8cally turned into a int variable name under <package_name>.R.<resource_type> We call it “Resource ID”

R.drawable.ic_launcher

Ic_launcher.png

Remember !

Rule 12: Filename (ext not included) in resource folder will be turned into a variable name in Java. So you can’t use some character in the filename (for example, - +)

Rule 13: Never has the same filename in the same folder although they are in the different file type (for example: icon1.jpg, icon1.png)

Resources Type: Layout

• A layout resource defines the architecture for the UI in an Ac8vity or a component of a UI. •  Folder res/layout

The R class: How are Resources compiled? #2

Every single resource will be put in the same place with different assigned Resource ID automa8cally set by Android compiler

R.drawable.ic_launcher

ac8vity_main.xml

R.layout.ac8vity_main

android:id

•  Inside the layout xml file, you will find something like

android:id=“@+id/xxxx” or android:id=“@id/xxxx” •  It is simply a Resource ID referring to a View inside a Layout •  You have no need to assign it for every single element, just one you need to

reference

Rule 14: Don’t use the same ID in the single file, but feel free to use in any other file

Resources Type: Menu

• A menu resource defines an applica8on menu (Op8ons Menu, Context Menu, or submenu) that can be inflated with MenuInflater. •  Folder res/menu •  Learn more about Menus in Part

3

Resources Type: Values

•  Folder res/values • Be careful, Resource ID is not R.values.xxxx •  Look into each one by one •  Dimension •  String •  Colors

•  You will learn more by prac8ce all along this class

Resources Type: Anim

• View Anima8on • Creates an anima8on by performing a series of transforma8ons on a single

image or creates an anima8on by showing a sequence of images in order •  Folder res/anim •  Too complicated to talk about this now. See you later.

Resources Type: Animator

• Property Anima8on • Creates an anima8on by modifying an object's property values over a set

period of 8me •  Folder res/animator •  Too complicated to talk about this now. See you later.

Resources Type: The Rest

• Not so important • But once you know the concept of Resource, you will be able to learn more

about another type of resource by yourself in a minute

ConfiguraHon Qualifier

• ALERT: VERY IMPORTANT !!! • Very smart resource selec8on mechanic in Android •  Folder format

<resources_name>-<qualifier>

• Can be applied on any resource type •  For example

res/drawable-xhdpi res/layout-xxhdpi

ConfiguraHon Qualifier Type

•  dpi – ldpi, mdpi, hdpi, xhdpi, xxhdpi, xxxhdpi, nodpi, tvdpi •  Screen size – small, normal, large, xlarge • Width – w<N>dp (for example, w820dp) •  Smallest Width – sw<N>dp (for example, sw600dp) •  Screen aspect – long, not long •  PlaLorm version – v<N> (for example, v21) •  And a lot more •  So you might see something like drawable-notlong-land-xxxhdpi-xlarge-v21 … •  Have to do it by order, cannot shuffle the posi8on •  See more at

hpp://developer.android.com/guide/topics/resources/providing-resources.html#Alterna8veResources

ConfiguraHon Qualifier: Select by qualifier

•  If hardware’s configura8on matches the qualifier, resource inside that folder will be used

•  See an example

ConfiguraHon Qualifier

480x800 720x1200 960x1600

200x200

ConfiguraHon Qualifier: Auto Scale

• But if the folder doesn’t existed, it will look into the nearest configura8on and scale in the same way as dp !

•  For example, if image is decoded in xhdpi has 100 pixels width, when it is decoded in mdpi, its width will be at 50 pixels

•  In the other words, if you put 50x50 pixels image in drawable-mdpi, you will get the same size (but not quality) as you put 100x100 pixels image in drawable-xhdpi

•  See an example

x2

x1

ConfiguraHon Qualifier: List of Qualifier

• Very smart resource selec8on mechanic in Android •  Folder format

<resources_name>-<qualifier>

•  For example drawable-xhdpi

drawable-xxhdpi

Rule 15: With knowledge about dp and Configura8on Qualifier (and sure, with some prac8cing), you will 80% win over Fragmenta8on !

Do we need to define every single qualifier?

NO and DON’T !

Best PracHces: Drawable

• Put icon inside every single dpi qualifier in mipmap • Don’t put image files inside res/drawable and/or res/drawable-nodpi

unless you know what are you doing •  res/drawable is treated like res/drawable-mdpi •  Image put inside res/drawable-nodpi will be not scaled

• Put Drawable Resources inside just a single folder and let it be scaled automa8cally •  res/drawble-xhdpi is recommended (just by me)

•  (Cont.) unless you really need to customize for some screen (and you will need it) •  Mobile/Tablet (because I will let you do) •  Support for some high resolu8on screen (2K for example)

Best PracHces: Layout

•  Since dp is all the same in any single dpi, so you have no need to put anything axer layout folder •  Just use res/layout

• Unless you need to customize the screen for Landscape Handset or for Tablet •  Use res/layout-land for Landscape •  Use res/layout-sw600dp for Tablet screen •  Use res/layout-sw600dp-land for Landscape Tablet screen •  And it is mostly what we do for layout already …

Best PracHces: Layout

• And you will need to do that as well … (separated Layout for Tablet)

Rule 16: Be lean, don’t have too many qualifiers. It causes more problem rather than helping.

How to access resource from Java?: The Context

“Interface to global informa8on about an applica8on environment”

If you want to access to anything -  Applica8on’s Resources -  Launch Ac8vity -  Send Broadcast -  Receive Intent -  Get Screen Resolu8on -  A lot !!

* Context is one of the thing you will see the most in Android App Development, be used to it

How to access resource from Java?

•  context.findViewById(…) •  context.getResources(…) • Curious why do we can call those methods without calling through context? • And what’s about setText(R.string.xxx) ?

… Play Play Play …

Rule 16: Context is always be used everywhere. Have a date with it everyday from now on.